Dear All,
Thanks a lot for your reply but I'm little bit lost.
We're often using Lev II for sampling and 0,065% for Critical defects, 2,5% for Major defects and 4,0% for Minor defects.
We made an inspection with following results:
Lot size: 3600 pieces
Sampling size: 200 pieces
Defects found
Critical: 0 agains 0 tolerated
Major: 12 against 10 tolerated
Minor: 14 against 14 tolerated
As a result the lot failed.
But, still with the same conditions the 2nd sampling done just after the 1st one give a better result.
Lot size: 3600 pieces
Sampling size: 200 pieces
Defects found
Critical: 0 agains 0 tolerated
Major: 4 against 10 tolerated
Minor: 12 against 14 tolerated
I'm aware that this is the risk of random sampling (accept bad lots / refuse good lots).
And it is very difficult to make understand this to our client. They don't want to understand this and I need to give them a better explanation.
Is there any calculation that can give to me the possible deviation?
How can I draw OC curves for above examples?
Thanks again for your help this helped me to understand better the concept.